src/or/rendmid.c

   1 /* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
   2  * Copyright (c) 2007-2013, The Tor Project, Inc. */
   3 /* See LICENSE for licensing information */
   4
   5 /**
   6  * \file rendmid.c
   7  * \brief Implement introductions points and rendezvous points.
   8  **/
   9
  10 #include "or.h"
  11 #include "circuitlist.h"
  12 #include "circuituse.h"
  13 #include "config.h"
  14 #include "relay.h"
  15 #include "rendmid.h"
  16 #include "rephist.h"
  17
  18 /** Respond to an ESTABLISH_INTRO cell by checking the signed data and
  19  * setting the circuit's purpose and service pk digest.
  20  */
  21 int
  22 rend_mid_establish_intro(or_circuit_t *circ, const uint8_t *request,
  23                          size_t request_len)
  24 {
  25   crypto_pk_t *pk = NULL;
  26   char buf[DIGEST_LEN+9];
  27   char expected_digest[DIGEST_LEN];
  28   char pk_digest[DIGEST_LEN];
  29   size_t asn1len;
  30   or_circuit_t *c;
  31   char serviceid[REND_SERVICE_ID_LEN_BASE32+1];
  32   int reason = END_CIRC_REASON_INTERNAL;
  33
  34   log_info(LD_REND,
  35            "Received an ESTABLISH_INTRO request on circuit %u",
  36            (unsigned) circ->p_circ_id);
  37
  38   if (circ->base_.purpose != CIRCUIT_PURPOSE_OR || circ->base_.n_chan) {
  39     log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
  40          "Rejecting ESTABLISH_INTRO on non-OR or non-edge circuit.");
  41     reason = END_CIRC_REASON_TORPROTOCOL;
  42     goto err;
  43   }
  44   if (request_len < 2+DIGEST_LEN)
  45     goto truncated;
  46   /* First 2 bytes: length of asn1-encoded key. */
  47   asn1len = ntohs(get_uint16(request));
  48
  49   /* Next asn1len bytes: asn1-encoded key. */
  50   if (request_len < 2+DIGEST_LEN+asn1len)
  51     goto truncated;
  52   pk = crypto_pk_asn1_decode((char*)(request+2), asn1len);
  53   if (!pk) {
  54     reason = END_CIRC_REASON_TORPROTOCOL;
  55     log_warn(LD_PROTOCOL, "Couldn't decode public key.");
  56     goto err;
  57   }
  58
  59   /* Next 20 bytes: Hash of rend_circ_nonce | "INTRODUCE" */
  60   memcpy(buf, circ->rend_circ_nonce, DIGEST_LEN);
  61   memcpy(buf+DIGEST_LEN, "INTRODUCE", 9);
  62   if (crypto_digest(expected_digest, buf, DIGEST_LEN+9) < 0) {
  63     log_warn(LD_BUG, "Internal error computing digest.");
  64     goto err;
  65   }
  66   if (tor_memneq(expected_digest, request+2+asn1len, DIGEST_LEN)) {
  67     log_warn(LD_PROTOCOL, "Hash of session info was not as expected.");
  68     reason = END_CIRC_REASON_TORPROTOCOL;
  69     goto err;
  70   }
  71   /* Rest of body: signature of previous data */
  72   note_crypto_pk_op(REND_MID);
  73   if (crypto_pk_public_checksig_digest(pk,
  74                                        (char*)request, 2+asn1len+DIGEST_LEN,
  75                                        (char*)(request+2+DIGEST_LEN+asn1len),
  76                                        request_len-(2+DIGEST_LEN+asn1len))<0) {
  77     log_warn(LD_PROTOCOL,
  78              "Incorrect signature on ESTABLISH_INTRO cell; rejecting.");
  79     reason = END_CIRC_REASON_TORPROTOCOL;
  80     goto err;
  81   }
  82
  83   /* The request is valid.  First, compute the hash of Bob's PK.*/
  84   if (crypto_pk_get_digest(pk, pk_digest)<0) {
  85     log_warn(LD_BUG, "Internal error: couldn't hash public key.");
  86     goto err;
  87   }
  88
  89   crypto_pk_free(pk); /* don't need it anymore */
  90   pk = NULL; /* so we don't free it again if err */
  91
  92   base32_encode(serviceid, REND_SERVICE_ID_LEN_BASE32+1,
  93                 pk_digest, REND_SERVICE_ID_LEN);
  94
  95   /* Close any other intro circuits with the same pk. */
  96   c = NULL;
  97   while ((c = circuit_get_intro_point((const uint8_t *)pk_digest))) {
  98     log_info(LD_REND, "Replacing old circuit for service %s",
  99              safe_str(serviceid));
 100     circuit_mark_for_close(TO_CIRCUIT(c), END_CIRC_REASON_FINISHED);
 101     /* Now it's marked, and it won't be returned next time. */
 102   }
 103
 104   /* Acknowledge the request. */
 105   if (relay_send_command_from_edge(0, TO_CIRCUIT(circ),
 106                                    RELAY_COMMAND_INTRO_ESTABLISHED,
 107                                    "", 0, NULL)<0) {
 108     log_info(LD_GENERAL, "Couldn't send INTRO_ESTABLISHED cell.");
 109     goto err;
 110   }
 111
 112   /* Now, set up this circuit. */
 113   circuit_change_purpose(TO_CIRCUIT(circ), CIRCUIT_PURPOSE_INTRO_POINT);
 114   circuit_set_intro_point_digest(circ, (uint8_t *)pk_digest);
 115
 116   log_info(LD_REND,
 117            "Established introduction point on circuit %u for service %s",
 118            (unsigned) circ->p_circ_id, safe_str(serviceid));
 119
 120   return 0;
 121  truncated:
 122   log_warn(LD_PROTOCOL, "Rejecting truncated ESTABLISH_INTRO cell.");
 123   reason = END_CIRC_REASON_TORPROTOCOL;
 124  err:
 125   if (pk) crypto_pk_free(pk);
 126   circuit_mark_for_close(TO_CIRCUIT(circ), reason);
 127   return -1;
 128 }
 129
 130 /** Process an INTRODUCE1 cell by finding the corresponding introduction
 131  * circuit, and relaying the body of the INTRODUCE1 cell inside an
 132  * INTRODUCE2 cell.
 133  */
 134 int
 135 rend_mid_introduce(or_circuit_t *circ, const uint8_t *request,
 136                    size_t request_len)
 137 {
 138   or_circuit_t *intro_circ;
 139   char serviceid[REND_SERVICE_ID_LEN_BASE32+1];
 140   char nak_body[1];
 141
 142   log_info(LD_REND, "Received an INTRODUCE1 request on circuit %u",
 143            (unsigned)circ->p_circ_id);
 144
 145   if (circ->base_.purpose != CIRCUIT_PURPOSE_OR || circ->base_.n_chan) {
 146     log_warn(LD_PROTOCOL,
 147              "Rejecting INTRODUCE1 on non-OR or non-edge circuit %u.",
 148              (unsigned)circ->p_circ_id);
 149     goto err;
 150   }
 151
 152   /* We could change this to MAX_HEX_NICKNAME_LEN now that 0.0.9.x is
 153    * obsolete; however, there isn't much reason to do so, and we're going
 154    * to revise this protocol anyway.
 155    */
 156   if (request_len < (DIGEST_LEN+(MAX_NICKNAME_LEN+1)+REND_COOKIE_LEN+
 157                      DH_KEY_LEN+CIPHER_KEY_LEN+PKCS1_OAEP_PADDING_OVERHEAD)) {
 158     log_warn(LD_PROTOCOL, "Impossibly short INTRODUCE1 cell on circuit %u; "
 159              "responding with nack.",
 160              (unsigned)circ->p_circ_id);
 161     goto err;
 162   }
 163
 164   base32_encode(serviceid, REND_SERVICE_ID_LEN_BASE32+1,
 165                 (char*)request, REND_SERVICE_ID_LEN);
 166
 167   /* The first 20 bytes are all we look at: they have a hash of Bob's PK. */
 168   intro_circ = circuit_get_intro_point((const uint8_t*)request);
 169   if (!intro_circ) {
 170     log_info(LD_REND,
 171              "No intro circ found for INTRODUCE1 cell (%s) from circuit %u; "
 172              "responding with nack.",
 173              safe_str(serviceid), (unsigned)circ->p_circ_id);
 174     goto err;
 175   }
 176
 177   log_info(LD_REND,
 178            "Sending introduction request for service %s "
 179            "from circ %u to circ %u",
 180            safe_str(serviceid), (unsigned)circ->p_circ_id,
 181            (unsigned)intro_circ->p_circ_id);
 182
 183   /* Great.  Now we just relay the cell down the circuit. */
 184   if (relay_send_command_from_edge(0, TO_CIRCUIT(intro_circ),
 185                                    RELAY_COMMAND_INTRODUCE2,
 186                                    (char*)request, request_len, NULL)) {
 187     log_warn(LD_GENERAL,
 188              "Unable to send INTRODUCE2 cell to Tor client.");
 189     goto err;
 190   }
 191   /* And sent an ack down Alice's circuit.  Empty body means succeeded. */
 192   if (relay_send_command_from_edge(0,TO_CIRCUIT(circ),
 193                                    RELAY_COMMAND_INTRODUCE_ACK,
 194                                    NULL,0,NULL)) {
 195     log_warn(LD_GENERAL, "Unable to send INTRODUCE_ACK cell to Tor client.");
 196     circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_INTERNAL);
 197     return -1;
 198   }
 199
 200   return 0;
 201  err:
 202   /* Send the client an NACK */
 203   nak_body[0] = 1;
 204   if (relay_send_command_from_edge(0,TO_CIRCUIT(circ),
 205                                    RELAY_COMMAND_INTRODUCE_ACK,
 206                                    nak_body, 1, NULL)) {
 207     log_warn(LD_GENERAL, "Unable to send NAK to Tor client.");
 208     /* Is this right? */
 209     circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_INTERNAL);
 210   }
 211   return -1;
 212 }
 213
 214 /** Process an ESTABLISH_RENDEZVOUS cell by setting the circuit's purpose and
 215  * rendezvous cookie.
 216  */
 217 int
 218 rend_mid_establish_rendezvous(or_circuit_t *circ, const uint8_t *request,
 219                               size_t request_len)
 220 {
 221   char hexid[9];
 222   int reason = END_CIRC_REASON_TORPROTOCOL;
 223
 224   log_info(LD_REND, "Received an ESTABLISH_RENDEZVOUS request on circuit %u",
 225            (unsigned)circ->p_circ_id);
 226
 227   if (circ->base_.purpose != CIRCUIT_PURPOSE_OR) {
 228     log_warn(LD_PROTOCOL,
 229              "Tried to establish rendezvous on non-OR circuit with purpose %s",
 230              circuit_purpose_to_string(circ->base_.purpose));
 231     goto err;
 232   }
 233
 234   if (circ->base_.n_chan) {
 235     log_warn(LD_PROTOCOL,
 236              "Tried to establish rendezvous on non-edge circuit");
 237     goto err;
 238   }
 239
 240   if (request_len != REND_COOKIE_LEN) {
 241     log_fn(LOG_PROTOCOL_WARN,
 242            LD_PROTOCOL, "Invalid length on ESTABLISH_RENDEZVOUS.");
 243     goto err;
 244   }
 245
 246   if (circuit_get_rendezvous(request)) {
 247     log_warn(LD_PROTOCOL,
 248              "Duplicate rendezvous cookie in ESTABLISH_RENDEZVOUS.");
 249     goto err;
 250   }
 251
 252   /* Acknowledge the request. */
 253   if (relay_send_command_from_edge(0,TO_CIRCUIT(circ),
 254                                    RELAY_COMMAND_RENDEZVOUS_ESTABLISHED,
 255                                    "", 0, NULL)<0) {
 256     log_warn(LD_PROTOCOL, "Couldn't send RENDEZVOUS_ESTABLISHED cell.");
 257     reason = END_CIRC_REASON_INTERNAL;
 258     goto err;
 259   }
 260
 261   circuit_change_purpose(TO_CIRCUIT(circ), CIRCUIT_PURPOSE_REND_POINT_WAITING);
 262   circuit_set_rendezvous_cookie(circ, request);
 263
 264   base16_encode(hexid,9,(char*)request,4);
 265
 266   log_info(LD_REND,
 267            "Established rendezvous point on circuit %u for cookie %s",
 268            (unsigned)circ->p_circ_id, hexid);
 269
 270   return 0;
 271  err:
 272   circuit_mark_for_close(TO_CIRCUIT(circ), reason);
 273   return -1;
 274 }
 275
 276 /** Process a RENDEZVOUS1 cell by looking up the correct rendezvous
 277  * circuit by its relaying the cell's body in a RENDEZVOUS2 cell, and
 278  * connecting the two circuits.
 279  */
 280 int
 281 rend_mid_rendezvous(or_circuit_t *circ, const uint8_t *request,
 282                     size_t request_len)
 283 {
 284   or_circuit_t *rend_circ;
 285   char hexid[9];
 286   int reason = END_CIRC_REASON_INTERNAL;
 287
 288   if (circ->base_.purpose != CIRCUIT_PURPOSE_OR || circ->base_.n_chan) {
 289     log_info(LD_REND,
 290              "Tried to complete rendezvous on non-OR or non-edge circuit %u.",
 291              (unsigned)circ->p_circ_id);
 292     reason = END_CIRC_REASON_TORPROTOCOL;
 293     goto err;
 294   }
 295
 296   if (request_len != REND_COOKIE_LEN+DH_KEY_LEN+DIGEST_LEN) {
 297     log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
 298          "Rejecting RENDEZVOUS1 cell with bad length (%d) on circuit %u.",
 299          (int)request_len, (unsigned)circ->p_circ_id);
 300     reason = END_CIRC_REASON_TORPROTOCOL;
 301     goto err;
 302   }
 303
 304   base16_encode(hexid, sizeof(hexid), (const char*)request, 4);
 305
 306   log_info(LD_REND,
 307            "Got request for rendezvous from circuit %u to cookie %s.",
 308            (unsigned)circ->p_circ_id, hexid);
 309
 310   rend_circ = circuit_get_rendezvous(request);
 311   if (!rend_circ) {
 312     log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
 313          "Rejecting RENDEZVOUS1 cell with unrecognized rendezvous cookie %s.",
 314          hexid);
 315     reason = END_CIRC_REASON_TORPROTOCOL;
 316     goto err;
 317   }
 318
 319   /* Send the RENDEZVOUS2 cell to Alice. */
 320   if (relay_send_command_from_edge(0, TO_CIRCUIT(rend_circ),
 321                                    RELAY_COMMAND_RENDEZVOUS2,
 322                                    (char*)(request+REND_COOKIE_LEN),
 323                                    request_len-REND_COOKIE_LEN, NULL)) {
 324     log_warn(LD_GENERAL,
 325              "Unable to send RENDEZVOUS2 cell to client on circuit %u.",
 326              (unsigned)rend_circ->p_circ_id);
 327     goto err;
 328   }
 329
 330   /* Join the circuits. */
 331   log_info(LD_REND,
 332            "Completing rendezvous: circuit %u joins circuit %u (cookie %s)",
 333            (unsigned)circ->p_circ_id, (unsigned)rend_circ->p_circ_id, hexid);
 334
 335   circuit_change_purpose(TO_CIRCUIT(circ), CIRCUIT_PURPOSE_REND_ESTABLISHED);
 336   circuit_change_purpose(TO_CIRCUIT(rend_circ),
 337                          CIRCUIT_PURPOSE_REND_ESTABLISHED);
 338   circuit_set_rendezvous_cookie(circ, NULL);
 339
 340   rend_circ->rend_splice = circ;
 341   circ->rend_splice = rend_circ;
 342
 343   return 0;
 344  err:
 345   circuit_mark_for_close(TO_CIRCUIT(circ), reason);
 346   return -1;
 347 }
 348